Conventional rotatory drilling as practiced for many years has required the use of a rotary table containing an opening through which a non-circular kelly pipe extends for engagement with a kelly bushing mounted in the table, driving the kelly bushing and connected drill string rotatively while permitting downward advancement of the kelly relative to the table.
In recent years, an alternative drilling system has a drilling unit having a section of pipe connectable to the upper end of the drill string and a motor for driving the pipe rotatively to turn the string. The entire powered drilling assembly may then move upwardly and downwardly with the string to drive the string very directly and positively and without the necessity for a kelly and kelly bushing-type connection. This type of system is called a “top drive” drilling system.
In such a top drive drilling system, there is substituted for the usual rotary table, kelly, and related equipment, an assembly which is connected to the upper end of the drill string which moves upwardly and downwardly therewith and has a motor driving a rotary element or stem connected to the string and acting to turn it. The powered top drive assembly is usually guided in its upward and downward movement by tracks or guide elements fixed to the rig derrick or mast.
FIG. 1 illustrates a conventional prior art top drive drilling system. The top drive drilling rig 10 has the usual derrick 11 having a rig floor 12 containing an opening 13 through the which the drill string 14 extends downwardly into the earth 15 to drill a well 16. The drill string is formed of a series of pipe connections interconnected at threaded joint 17 and having a bit at the lower end of the string. At vertically spaced locations, the string has stabilizer portions which may include stabilizer elements 18 extending helically along the outer surface of the string to engage the wellbore wall in a manner centering the drill string therein.
The string is turned by a top drive drilling unit 19 which is connected to the upper end of the string and moves upwardly and downwardly therewith along the vertical axis 20 of the well. A pipe handler assembly 21 is suspended from the drilling unit. The drilling unit 19 has a swivel 22 at its upper end to which drilling fluid is introduced into the string, and by which the unit is suspended from a traveling block 23 which is suspended and moved upwardly and downwardly by a line 24 connected at its upper end to a crown block 25 and actuated by the usual drawworks 26. The drilling unit 19, pipe handler 21 and connected parts are guided for vertical movement along axis 20 by two vertical guide rails or tracks 27 rigidly attached to derrick 11. The drilling unit 19 is attached to a carriage 28 having rollers engaging and located by rails and guided by those rails for vertical movement upwardly and downwardly along the rails parallel to axis 20. The top drive drilling unit 19 includes a housing 30 which is connected to the carriage 28 in fixed position relative thereto during drilling and round tripping operations. A motor is positioned so as to suitably drive the drill string. Conventionally, this motor is an AC or DC motor which receives a power supply for the rotational capabilty. Typical transmission systems are integrated in association with the motor so as to provide the requisite torque for the rotation of the drill string. As such, the motor is actually indirectly interconnected to the drill string.
In the past, various patents have issued relating to such top drive systems. For example, U.S. Pat. No. 4,437,524, issued on Mar. 20, 1984 to Boyadjieff et al., shows a well drilling system that has a drilling unit with a tubular part connectible to the upper end of the drill string and a motor for driving that tubular part rotatively. The drilling unit is mounted by a guide structure for vertical movement.
U.S. Pat. No. 4,449,596 issued on May 22, 1984 to Boyadjieff, shows a well drilling apparatus having a top drive drilling assembly with a motor driven stem adapted to be attached to the upper end of a drill string. A torque wrench is carried by the top drive assembly and movable upwardly and downwardly therewith and operable so as to break a threaded connection between the drill string and the stem. An elevator is carried by and suspended from the top drive assembly and adapted to engage a section of drill pipe beneath the torque wrench in suspending relation.
U.S. Pat. No. 4,529,045, issued on Jul. 16, 1985 to Boyadjieff et al., teaches a top drive well drilling unit which is connected to the upper end of a drill string to drive it rotatively in drilling a well. The drilling unit is movable upwardly and downwardly with the string along a guide structure. A pipe handling mechanism is provided beneath the drilling unit for making and breaking a threaded connection between the drilling unit and the string. The pipe handling mechanism is retained against rotation with the drill string during a drilling operation, but is constructed to allow rotation of the elevator and a suspended string relative to the drilling unit when the string is supported by the elevator without connection to the drilling unit.
U.S. Pat. No. 4,605,077, issued on Aug. 12, 1986 to Boyadjieff, describes a top drive drilling system having a motor which is connected to the upper end of the drill string and moves upwardly and downwardly therewith. This top drive drilling system enables the drill string to be pulled upwardly off of the bottom of the well each time an additional length of drill pipe is added to the string. The connection between that added length and the upper end of the string is made at an elevated location spaced above the rig floor. An elevated platform is provided on which a person may move to a location near the raised upper end of the string for assisting in making the connection.
U.S. Pat. No. 7,055,594, issued on Jun. 6, 2006 to Springett et al., shows a top drive drilling system having a top drive unit and a pipe gripping system beneath the top drive unit. The pipe gripping system has an open throat for receiving a tubular to be gripped by the pipe gripping system. The gripping system has a body with first and second jaws movably connected thereto and piston/cylinder devices movably interconnected with each jaw for moving the jaws to clamp and then to rotate the pipe.
U.S. Pat. No. 7,188,686, issued on Mar. 13, 2007 to Folk et al., describes a top drive system for wellbore operations that includes a hollow bore alternating current permanent magnet motor with a motor bore therethrough. A planetary gear system is coupled to the motor. The gear system has a gear system bore therethrough. A quill is drivingly connected to the planetary gear system and rotatable thereby to rotate a tubular member located below the quill. The motor adjacent the gear system is aligned with the gear system bore so that fluid is flowable through the top drive system from the top of the motor to the bottom of the planetary gear system and into and through the quill.
U.S. Pat. No. 7,401,664, issued on Jul. 22, 2008 to Wells et al., describes a top drive system having a motor apparatus and a main shaft driven by the motor apparatus. The main shaft has a top end and a bottom end. A quill is connected to the main shaft. A gear system is interconnected with the quill and the motor apparatus.
U.S. Pat. No. 7,419,012, issued on Sep. 2, 2008 to Lynch, describes a drive system for wellbore operations having a main body, a motor apparatus, and a main shaft extending from the main body and rotatable by the motor. The main shaft has a top end and a bottom end. A structure is non-threadedly connected to the main shaft.
One of the problems with prior art top drive systems is the utilization of an indirectly interconnected motor and gearing system to the drill stem. The motor and the associated gear system are extremely heavy. In order to achieve the requisite torque, very large and complicated gearing systems are required. Unfortunately, because of the large size of the motor and gearing systems, the entire system cannot be easily transported on road systems. Typically, the motor and the associated gearing system must be transported as separate items along the roads and then assembled on site. The assembly process becomes very complicated and extreme precision is required so as to properly integrate the motor with the gearing system and with the drill string. In view of the relatively large nature of these systems, the AC motor that is associated with such systems has an extremely large rotor. As such, there are strong inertial effects whenever the motor is rotating. In other words, the large inertial effects can cause difficulty in breaking the operation of the motor. In typical use, one type of motor and associated gearing system are required for a top drive system, another motor and associated gear system is required for the drawworks, and still a further motor and gearing system is associated with the mud pumping mechanism. As such, a need has developed so as to provide a lower weight, greater power density motor that can be easily transported as a single unit on road systems.
It is an object of the present invention to provide a direct drive top drive motor that requires no gearing mechanism.
It is another object of the present invention to provide a direct drive top drive motor that has a very high power density.
It is still another object of the present invention to provide a direct drive top drive system which is relatively light weight.
It is still a further object of the present invention to provide a direct drive top drive system that can be easily transported on conventional road systems.
It is a further object of the present invention to provide a direct drive top drive system which requires no assembly or precision installation in the field.
It is still another object of the present invention to provide a direct drive top drive system that has reduced inertial effects.
It is still another object of the present invention to provide a direct drive top drive system that utilizes a motor that can be easily interchanged between use in association with the top drive, the mud pump and the drawworks.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.